SB 

j;^ U. S. DEPARTMENT OF AGRICULTURE. 

• U^ BUREAU OF PLANT INDUSTRY— BULLETIN NO. 167. 



B. T. GALLOWAY, Chief of Bureau. 



NEW METHODS OF PLANT BREEDING 



GEORGE W. OLIVER, Plant Propagator. 



Issued Februaky 7, 1910. 





WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
1910. 



U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 167. 

B. T. GALLOWAY, Chief of Bureau. 



NEW METHODS OF PLANT BREEDING. 



GECmOE W. OLIVER, Plant Propagator. 



Issued Feukuakv 7, I'JIO. 




WASHINGTON: 

GOVKRNMKNT PRINTING OFFICE. 
1!> 1 U . 



'O'- 



BUREAU OF PLANT INDUSTRY. 



Chic/ of Bureau, Beverly T. CJalloway. 
Assistant Chief of Bureau, Albert F. Woods. 
Editor, J. E. Rockwell. 
Chief Clerk, James K. Jones. 



Foreign Seed and I'lant Introduction. 

SCIENTIFIC staff. 

David Fairchild, Agricultural Explorer in Charge. 
P. H. Dorsett, Albert Mann, George W. Oliver, Walter Van Fleet, and Peter Bisset, Experts. 
Frank N. Meyer, Agricultural Explorer. 
H. V. Harlan, H. C. Skeels, and R. A. Young, Assistants. 
Edward Gouelier and P. J. Wester, Assistant Propagators. 

167 
2 



peg 11 1910 



a^^^ 10- 2 



^C^r" 






LHTTHK OF TRANSMITTAL 



U. S. Department of Agriculture, 

Bureau of Plant Industry, 

Office of the Chief, 
Washington, D. C, Septemher 25, 1909. 
Sir: I have the honor to transmit herewith a manuscript entitled 
•'New Methods of Plant Bi-eeding," by Mr. Georj^e W. Oliver, Plant 
Propagator of this Bureau, and recommend that it be ])ublishe(l as 
Bulletin No. 167 of the Bureau series. 

Respectfully, B. T. Galloway, 

Chief of Bureau. 
Hon. James Wilson, 

Secretary of Agriculture. 

167 3 



CONTENTS' 



Page. 

Introduction 7 

Origin of the new methods of plant breeding 8 

Tools required for depollinatiou and emasculation 11 

Devices used in depollinating flowers 12 

Emasculation 13 

Obstacles in emasculating the flowers of Compositsp 18 

How hybrids and crosses of composite flowers may have originated in the past. 14 

Preparation of seed and pollen bearing parents ]5 

Condition of the stigma at the time of pollination 16 

The application of water to all flowers 16 

Crossing alfalfa 16 

Work accomplished in the past 16 

Peculiar features of the work 17 

Old methods of crossing alfalfa 18 

New methods devised by the writer 18 

Depollinatiou by water 18 

Depollinatiou by compressed air 22 

The growing of the plants and their care 22 

Raising large quantities of seed from a cross 23 

Crossing large-flowered legumes 23 

Crossing in large and small numl:)ers 25 

Hybridizing species 26 

Helianthus hybrids 26 

Grass hybrids 27 

Crossing cultivated varieties on natural species 28 

Pansies 28 

Dahlias 28 

Cross-pollinating clovers 29 

Methods of emasculating and pollinating common flowers 30 

The essential organs of the flower 30 

Preparation of flowers to be pollinated 30 

Removal of the anthers 31 

Securing pollen 32 

Applying the pollen to the stigma 32 

Description of plates 33 

Index 35 

167 r> 



ILLUSTRATIONS. 



PLATES. 

Page. 
Plate I. Fi<r. 1. — Staminal tubes and stigmas of lettuce flowers. Fig. 2. — 

Depollinating lettuce flowers with water from a garden hose 34 

II. Fig. 1. — Flowers of alfalfa, showing the method of depollinating* and 

crossing used. Fig. 2. — Raceme of alfalfa flowers 34 

III. Sexual columns of alfalfa flowers, showing different stages of develop- 

ment 34 

IV. Fig. 1. — Flowers and young pods of the cowpea. Fig. 2. — Seeds of 

cowpea parents and of a first-generation cross 34 

V. Fig. I. — Dahlia chisolmii, showing disk florets before depollination. 
Fig. 2. — Dahlia chisolmii, showing disk florets after depollination 
by a jet of water 34 

VI. Fig. 1. — Disk florets of the greenhouse cineraria before depollination, 
showing the stigmas covered with pollen. Fig. 2. — Disk florets of 

the greenhouse cineraria after depollination with water 34 

VII. Fig. 1.— Flower of dahlia, showing the disk florets, the stigmas of 
which are nearly all covered with pollen. Fig. 2. — The dahlia 
flower shown in figure 1, with the outer florets depollinated by a 

jet of water 34 

VIII. Fig. 1.— Dahlia florets, showing development of the stigmas. Fig. 

2.— Dahlia florets, before and after depollination 34 

IX. Fig. 1.— Disk florets of Ilelianthus, showing different stages of devel- 
opment. Fig. 2. — Flowers of Canna indica, showing stamen and 

pistil in different stages of development 34 

X. Fig. 1.— Flowers of Plantago lanceolata, showing pistils maturing 
before the stamens. Fig. 2.— Flower of Campanula rotundifolia, 
showing stamens maturing before the pistil 34 

XI. Fig. 1.— Single tea rose, showing how easily hermaphrodite flowers 
having large stamens may be emasculated. Fig. 2. — Flowers of 

roses, showing method of emasculation 34 

XII. Fig. 1.— Flowers (monoecious) of the begonia, showing the sexes in 
different flowers on the same plant. Fig. 2.— Staminate and pistil- 
late flowers of Codiaeum variegatum from the same plant 34 

XIII. Fig. 1.— Staminate and pistillate (dioecious) flowers of willow, from 

different plants. Fig. 2.— Flowers from staminate and jiistillate 

plants of Asparagus officinalis 34 

XIV. Flowers from first-generation seedlings of crosses of pansies 34 

XV. Single branch of hybrid dahlia plant -^4 

TEXT I'IGURES. 

Fig. 1. Tools used in depollination and emasculation - H 

2. Devices used in the depollination of flowers 12 

167 
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B. P. I.— 516. 



NEW METHODS OF PLANT BREEDING. 



INTRODUCTION. 

A few years ago Dr. B. T. Galloway, Chief of the Bureau of Plant 
Industry, mapped out some plant-breeding work for the writer which 
involved crossing varieties of lettuce, alfalfa, and cowpea, and also 
certain species of Poa, Trifolium, Melilotus, etc. The work in the 
beginning presented many difhculties which have since been over- 
come, and it is now progressing satisfactorily. 

The improvement of plants by cross-breeding varieties is gradually 
becoming an important factor in the culture of many of our field and 
garden crops. The majority of intentional crosses and hybrids made 
in the past represent work which has been easy of accomplishment^ 
The more diflicult subjects luive been passed by or at most the efforts 
of breeders with the hitherto refractory genera have to a large extent 
been nullified by natural obstacles in the path of success. 

The only difUcult part of plant breeding lies in knowing just how 
to make the most of a cross or hybrid which has been seciu'ed. The 
literature on this subject which has appeared during the last few 
years is apt, unfortunately, to lead the beginner and even the prac- 
tical breeder into a maze, and he may conclude that the subject is 
too complex for comprehension. 

This should not cause discouragement, however, because the mission 
of the plant breeder is to produce varieties wliich are in some measure 
improvements over the old ones, and each advance made will tend 
tow^ard that perfecting of plant life which will insure better products 
for man and the domestic animals. 

The present contribution to the subject deals not with laws, but 
with methods used by the writer in accomplishing what have hitherto 
been considered impossible or difhcult crosses, and they may prove 
helpful to others engaged in the same line of work. 

Until recently it has been found impossible to cross many plants 
owing to the fragile nature of the sexual organs. This diiliculty has 
been removed, and the process whereby it has been accomplished is 
here described for the first time. 

There are numerous plants, also, both ornamental and economic, 
the flowers of wliich are so small that their stamens are very dilficult 

167 7 



8 NEW METHODS OF PLANT BREEDING. 

to remove in the process of emasculation, and this fact has undoubt- 
edly contributed largely toward delaying the rapid improvement of 
many flowering plants, fruits, and vegetables by cross-breeding and 
hybridizing. Mendel, who did so much in his particular line, worked 
with two genera only: Pisuni and Hieracium. The former is easy to 
manipulate, but all the species of Hieracium present difliculties in 
emasculation which by the ordinary methotls are practically insur- 
mountable. In fact, Mendel found them so great that he did not 
finish his work on this genus. Nevertheless, in tlie flowers of the 
hieraciums, and many other plants regarded as equally difficult, the 
pollen can be thoroughly removed, and with as great facility as in 
those of the rose or any other flower in which the reproductive organs 
are large and easily handled. This new process, which may be 
called "depollination," is the removal of pollen from the stigma 
before fecundation has taken place. It is applicable to flowers in 
which emasculation is impracticable because of the minuteness or 
delicacy of the floral organs. It is hoped that this newly found 
method of })reventing fecundation by undesirable pollen will be in- 
strumental in furthering the projects mapped out by the ever- 
increasing number of plant breeders. 

The writer has worked on several genera of the Composite^ with 
complete success. The method here described can be used not only 
with the Composittie, but also with all flowers having reproductive 
organs too smaU to be successfully manipulated by the ordinary 
methods of emasculation. The use of the method does not stop here. 
It can also be applied to the stigmas of larger flowers when there is 
any doubt whether pollen has recently gained access to the stigmas 
previous to artificial poflination. 

ORIGIN OF THE NEW METHODS OF PLANT BREEDING. 

During the spring of 1903 work was begun on the crossing of certain 
varieties of forcing lettuce. Wlien the plants came into flower it was 
at once apparent that the problem of emasculation was a knotty one. 
The flower heads are small and the florets themselves wifl scarcely 
bear handling because of their very fragile nature. In one or two 
instances the stamens were removed, but always with sufficient injury 
to the remaining parts of the flower to cause it to wither. A flower 
of lettuce is in fact about as difficult to manipulate by the usual 
methods of emasculation as it is possible to conceive. 

WTien the flower head expands, the anthers have already dehisced, 
and the unexpanded stigmas are covered with pollen. (See PL I, fig. 1 . ) 
The stigmas begin to expand at the tips, and sinudtaneously masses of 
pollen fall on the inner surfaces, to which the pollen closely adheres. 

167 



OKIGIN OF THE NEW METHODS OF PLANT BREEDING. 9 

In the bud stage the parts of the floret are so easily damaged that 
endeavors along this line of attack were quickly abandoned. Having 
read somewhere that pollen grains would adhere readily to the end of 
a piece of sealing wax previously rubbed briskly, wax was tried, but 
without success. The idea then suggested itself that the pollen 
might be successfully removed with a dampened camel's-hair brush. 
This plan was also a failure, because with the operation ever so care- 
fully performed some of the pollen grains were left on the stigmas. 

Success finally came, not with the aid of a camel's-hair brush or 
sealing wax, but with the aid of the garden hose. A robust plant of 
the Grand Rapids variety of lettuce opened 15 flowers one morn- 
ing, and within as many minutes every flower was successfully 
depollinated. The metal attachment on the end of the hose was cut 
off; a piece of hose of smaller diameter was placed in the end of the 
other hose; then a piece of soft rubber tubing of small diameter was 
placed inside the second piece of hose and the water turned on just 
enough to do a little more than trickle. By squeezing the end of the 
rubber tubing (see PI. I, fig. 2) a very tiny jet of water was secured. 
This was trained on the lettuce flowers, and perfect depollination 
resulted. 

After the tiny jets of water had played on each flower head foi' a 
few seconds not a trace of pollen was to be found and the pistils stood 
out from the ligules strong and unharmed. Small pieces of blotting 
paper freely applied to the florets edgewise soon absorbed all of the 
water. Pollen from the flower of another variety was then applied. 
In each of the 15 heads of flowers, seeds matured, and all of the result- 
ing seedlings proved to be intermediate between the two parents. 

In depollinating, the flower head is held securely between the 
thumb and the first and second fingers, and in pollinating it is simi- 
larly held. In applying the pollen to the stigmas one head of flowers 
from the pollen bearer is used, or more than one if suflicient pollen is 
not deposited on the stigmas. Before applying the ])ollen a few or 
all of the ligules should be cut off from the pollen-bearing head of 
flowers, leaving only the pollen-covered stigmas, and the remaining 
part of the head applied to the flowers which have been depollinated, 
working it among the stigmas with a circular motion. 

In pollinating lettuce flow^ers and those of other genera in this 
division of the Compositas there is not the same necessity for depositing 
the pollen on the stigma of each floret as there is on the flowers of the 
plants of the other divisions, because the lettuce flower heads close 
very soon after pollination. This act of closing will almost certainly 
cause the slender stigmas to become well covered with pollen liecause, 
in the act of jiollinating, the ligules are apt to harbor many grains 
of })()llen. 

TUT 



10 NEW METHODS OF PLANT BREEDING. 

The first cross effected was between the varieties of lettuce known 
as Grand Rapids and Golden Queen, the former being the seed bearer. 
A short account of the subsequent behavior of the seedlings may be 
of interest here as a guide to similar experiments in the futu'-e. 

The crossing was commenced about the beginning of Jul3^ From 
the application of pollen to the ripening of the seed, sixteen days 
elapsed, the time varying slightly according to the condition of the 
weather — warm, dry weather accelerating the ripening period. 

The seeds were sown in the latter part of December in order to make 
certain that the seedlings during the later stages of growth would 
have the benefit of warm weather and thus insure seed production. 

Seeds of each parent were also sown separately for comparison with 
the crosses in all stages of their growth. Even in the cotyledon stage 
differences were noted between the cot3'ledons of the crossed seeds 
and those of the parents; they were uniformly not as light in color 
as those of the Grand Rapids, neither were they as deep a yellow as 
those of the Golden Queen, but any doubt arising as to the differ- 
ences in color, size, and form of the cotyledons of the crosses com- 
pared with those of the parents was dispelled as soon as the first 
character leaves appeared in the crosses. The first leaf of the cross 
Grand Rapids X Golden Queen was similar in eveiy respect to the 
first leaf of the cross Golden Queen X Grand Ixapids, thus proving 
beyond a doubt at that early stage that the mere act of crossing had 
been a success. The plants of the two crosses could not have been 
distinguished, so similar were they in appearance. 

A large-sized Grand Rapids lettuce, but more yellowish in appear- 
ance than that variety, with the leaves slightly less crumpled and the 
margin less fringed, would be a fairly accurate description applicable 
to both lots of plants of the first-generation crosses. 

Seeds harvested from each of the plants were labeled and sown 
separately. In the second generation the results were rather be- 
wildering. The seeds from each plant of the first generation gave 
approximately 30 distinct forms, and out of the entire number of 
seedlings of the different numbers about 60 distinct forms were 
noted. Forty-five plants of these were selected for further testing, 
and it so happened that the plant numbered 39, selected as being 
the best in the field, gave the most promising progeny when sown 
indoors. Several were then selected for fixing. Four distinct forms 
have come true from seed in 1908. The fifth and last of the 
heading varieties up to that time had about 15 per cent of seedlings 
resembling the Grand Rapids variety. By selecting seed from each 
of 36 of the best heading individuals and sowing separately, about 
two-thirds of the lots have come true. These will be tested still 
further before being sent out for trial. 

167 



TOOLS FOE DEPOLLINATIOiSr AND EMASCULATION. 



11 



TOOLS REQUIRED FOR DEPOLLINATION AND EMASCULATION. 

A small pair of scissors is necessary to remove parts of corollas, 
stamens, etc., of the different flowers. Those shown in fio^iire 1, ^4, 
are more convenient for use on many subjects than the connnoii 
scissors, as they can very readily be adjusted to the various needs with 
one hand. A medium-sized pair of the ordinary kind of scissors 
used by plant breeders, with Ijlades 1 inch in leno;th, fij^ure 1, D, is 
also necessary. 

Forceps are indis])ensable tools. Those forceps in common use 
would be better adapted to the needs of the plant breeder were they 
supplied with a flat- 
tened pin attached to 
the handle (see fig. 1, 
C) . This would often 
prevent the necessity 
of la^nniz; down one 
tool to take up 
another while the op- 
erator is performing a 
dedicate piece of work 
and while the eyes are 
perhaps fixed on a 
very small object. A 
needle can be ti(>d on 
very easih" and the 
combination is an ex- 
ceedingly useful one. 
Several pairs of for- 
ceps which are self- 
closing (shown in fig. 
1, B) are necessary in 
such lines of work as 
pollinating depolli- 
nated stigmas of al- 
falfas and many other small flowers. These forceps enable the 
operator to hold a stamen or a sexual column of a small legume 
while pollinating. It is difficult to perform this work satisfactorily 
with the fuigers. 

Watch glasses and small-sized moist chambers are needed to pre- 
serve pollen. Tags for keeping records while the seeds are ripening, 
ranging from one-half inch by three-c(uarters inch to those of much 
larger dimensions, are indispensable. Some small-sized camel 's-hair 
brushes, some good white blotting paper torn into small ])ieces, and 
a lens should also be included in the kit. 

107 




Fig. 1.— Tools used in depollination and emasculation: A, scissors 
useful in removing small organs; JS, self-closing forceps; C, forceps 
with attachment; D, scissors for severing large organs. 



12 



NEW METHODS OF PLANT BREEDING, 



DEVICES USED IN DEPOLLINATING FLOWERS. 

The contrivances required for the work of depolhnation by water 
are inexpensive and easily secured. When the method was first 
used attachments to the garden hose were employed, but these were 
found too clumsy and uncertain; moreover, the hose is not always 
available when it is desired to depollinate flowers in the field. A 
fairly good substitute is a modification of the common putty bulb 
(fig. 2, E). This answers the purpose very satisfactorily for large 
flowers of the Composit??, Leguminosfe,and other groups. The putty 
bulb will hold about a pint of water. By imscrewing the spout or 

ejector, the rubber bag 
may be quickly filled 
with water and the 
ejector replaced in a 
few seconds. The size 
of the jet of water is 
regulated by using a 
suitable piece of ])am- 
boo reed or other con- 
trivance fixed firmly 
in the tube. When 
the l)idb is full of wa- 
ter a slight pressure 
with the hand will 
cause a fairly strong 
Init fine stream of wa- 
ter to be emitted. 

It will l)e found that 
a very small jet of wa- 
ter is needed for very 
small and fragile flow- 
ers. For this purpose 
the various kinds of 
chip blowers (fig. 2, 
A and B) and water bulbs sold by dental supply companies suit the 
plant breeder's needs admirably. These devices are inexpensive, and 
when many flowers are to be treated at one time several of the chip 
blowers or water bulbs may be brought into use. As soon as the 
contents of one are exhausted and while the bull) is still ])ressed in 
the hand it may be put in a vessel of water; then when the others 
are emptied of their contents the first one will be ready to l)e used 
again. 

There is a still further choice in instruments of this nature in the 
shape of rul)l)er bulbs (fig. 2, (^and D) similar to those used on cameras. 

1C7 




Fig. 2.— Devices used in the depollination of flowers: A and B, chip 
blowers or water bulbs; C, water bulb with valve at bottom pro- 
vided with celluloid ejector; D, old rubl>er bulb with glass tube 
inserted; E, " putty bulb" with attachment to give a small jet 
of water. 



OBSTACLES IN EMASCULATING ELOWEES OF COMPOSITiE. 13 

A piece of glass tubing can be pushed into one of these ; the other end 

of the tube can be brought to a fine point by heating it in a flame and 

breaking off the point, leaving an aperture about one-sixteenth inch 

in diameter. This device does satisfactory work, but the others 

are preferable. 

EM A SCUL ATION. 

A necessary preliminary to successful plant breeding by hybridiza- 
tion or cross-fertilization consists in preventing pollen of the plant 
used as the seed bearer, or pollen from other plants of the same 
variety or species, or pollen of any other closely allied variety or 
species from gaining access to the stigmatic surface of the flower 
intended to be pollinated instead of the pollen selected by the operator. 

With the greater number of plants, especially those having stamens 
of large size, emasculation is a simple matter, and consists of remov- 
ing the stamens before the anthers shed their })()lleii. Examples of 
plants having large stamens are found in the rose (see PI. XI, fig. 1), 
cherr}^, peach, etc. The l)opp>', carnation, and tobacco are also 
familiar examples in which emasculation is an exceedingly easy 
process, as the stamens can be removed Ix'foro dehiscing with a pair 
of forceps. 

OBSTACLES IN EMASCULATING THE FLOWERS OF COMPOSITiE. 

It is well known that the florets of the various genera of the com- 
posite flowers are so constructed that the anthers can not be removed 
without the florets being injured beyond recovery. 

The anthers in the disk florets unite and form a tid)e (PI. VIII, fig. 
1, B, and PI. IX, fig. \,B) over and around the upper part of the 
immature pistil so that in the effort to remove tliis tube before the 
floret opens or the anthers dehisce the anthers are certain to be rup- 
tured and the pollen scattered over the stigma. The parts of the 
florets are so small that it is practically impossible to remove the 
anthers in a young stage without ruining the florets. There is also 
great danger of injuring the Yevj slender pistils during the attempted 
emasculation. Some genera have only female organs in the ray 
florets and both male and female in the disk florets, and in some 
important genera some species have sterile ray florets and depend 
on the disk florets alone for fertilization. (PI. V, figs. 1 and 2.) But 
to depend on the ray florets alone for careful crossing means in all 
instances slipshod work, as the disk florets must then all be removed, 
causing too much mutilation of the flower head. Depollination of the 
disk florets by the method herein described (PI. VIII, fig. 2, B) means 
that the work is absolutely certain to produce the desired results. 
Moreover, depollination of the disk florets followed by crossing is many 
times easier than the use of the ray florets as seed bearers, as this is 

167 



14 NEW METHODS OF PLANT BREEDING. 

necessarily followed by the removal of the disk florets to prevent 
self-pollination. 

In several genera of the Compositse it will be found that the staminal 
tubes are not drawn down into the tubular corolla until the second 
day after shedding the pollen. This happens with some of the species 
of Helianthus (PL IX, fig. 1,B), Gaillardia, etc. A short, sharp needle 
fijfed in the end of a piece of wood less than the diameter of a pencil 
and 4 inches in length can be veiy successfully used in opening 
the collar formed by the united anthers around the stigma, so that 
it may be depollinated before the pollen grains germinate. All of 
the crop of florets wliich come out in any single day can be opened 
after the manner described, the pollen washed from them, and the 
flower head bagged, pollination being delayed until the following 
day, when the circles of florets contiguous to those already depollin- 
ated will have come to maturity. These are in turn treated with the 
needle and depollinated by water. The remaining unopened florets 
may then be pulled out with a pair of forceps, the two lots of treated 
stigmas pollinated at the same time, and the flower head bagged. 
A method still easier is to dej^ollinate the two outer circles of stigmas 
and then remove them with the aid of a pair of forceps, which in the 
larger number of genera is easy of accomj^lishment. When the 
remainder of the florets expand, depollination is effected and the 
flowers are pollinated as soon as the flower head is cleared of water 
(PI. VII, figs. 1 and 2). In all composite flowers wliich attract insects 
the head should be bagged to prevent undesirable pollen from gain- 
ing access to the stigmas after being pollinated. 

It may be said that unless the method of depollination herein 
described is used with flowers of the Compositne, especially those of 
the division Liguliflorse, there is very little chance, if any, of abso- 
lutely certain results from cross-fertilization between different varie- 
ties of the same species or from hybridizing distinct species, 

HOW HYBRIDS AND CROSSES OF COMPOSITE FLOWERS MAY 
HAVE ORIGINATED IN THE PAST. 

It is quite possible that a long continuous shower will wash the 
pollen from the stigmas of a composite flower and that as soon as the 
sun shines these flowers are visited by insects whose bodies are occa- 
sionally covered with pollen obtained from florets of other varieties 
or species which open and shed their pollen, either before or subse- 
quent to the pollen-removing shower of rain. It is certain that cross- 
fertilization may take place in this way. Those species and their 
varieties having infertile ray florets can be crossed only when the disk 
florets, containing both male and female organs, are used as the seed 
bearers. (PL VII, figs. 1 and 2.) All of the work in breeding compos- 
107 



PREPARATION OF SEED AND POLLEN BEARING PARENTS. 15 

ite flowers is rendered simple by the depollinating method. Especially 
is this the case with chrysanthemums, asters, dahlias (PL VI, fig. 2), 
marigolds, cineraria (PI. VI, fig. 1), cosmos, zinnias, lettuce, and with 
all the numerous genera having infertile ray florets, 

PREPARATION OF SEED AND POLLEN BEARING PARENTS. 

Too much care can not be bestowed on isolating from insects the 
plants from wliich pollen is to be selected for use in crossing. Tliis 
is a part of the plant "breeder's work wliich is apt to be neglected. 
PoUen is usually considered satisfactory irrespective of the condi- 
tions under wluch the flowers have been produced. It is not unna- 
turally supposed that the pollen is pure while the flowers are in the 
bud stage, and although this is the case in many instances, especially 
where large numbers of one variety or species are growing side by 
side, yet there is no doubt that the pollen of these plants is often 
interchanged, as in alfalfa and other plants of the legume family in 
-which the anthers dehisce in the flower bud and which are visited by 
the pollen-eating thrijis. 

Much experimental work in plant breeding b}^ crossing and hybridi- 
zation gives negative results through lack of care in the selection of 
pure pollen. It is just as necessary to protect the flower selected to 
supply the pollen, in order to prevent foreign pollen from being 
depositefl on or near the anthers either by insects or by wind, as it 
is to protect the seed-bearing flowers. In selecting pure pollen it is a 
good plan to have isolated plants growing in pots in the greenhouse, 
where they can be protected from insects during the flowering period 
by wire screens. If this is not feasible, the flowers should be bagged 
when the buds are nearing the opening stage, to prevent insects from 
depositing pollen on or near the flowers. Absolute success means 
careful attention to the very minutest detail. Omission of the neces- 
sary care in this respect has undoubtedly caused a vast amount of 
work to be unproductive of good results. Not only should the pollen 
bearer be grown under glass, but in every case where it is possible 
the seed-bearing parent should also be gro^\^l in this manner in order 
to have the work absolutely under control. Even then with the aid 
of wire screens only the large insects can be ke])t from the flowers as 
the pollen-eating thrips found in nearly all flowers is one of the 
greatest carriers of pollen from flower to flower. It is not unusual to 
find one of these minute insects with several grains of pollen attached 
to its body, rendering the work of evidently careful emasculation of 
no avail. The plants infested with these insects should be treated 
to a slight fumigation with hydrocyanic-acid gas and afterwards i)ro- 
tected with structures covered with some kind of fine white fabric to 
prevent the flowers being visited immediately before emasculation 
and until fertilization takes place. 

107 



16 NEW METHODS OF PLANT BREEDING. 

CONDITION OF THE STIGMA AT THE TIME OF POLLINATION. 

It has often been stated that the stigmatic surface of the pistil must 
be free from moisture when the pollen is applied. When the con- 
trary condition is present, the pollen is said to be less effective than 
it would be were it applied to the stigma when free from moisture 
deposited from the atmosphere. Be tliis as it may, it is absolutely 
certain that pollen is as effective when applied to stigmas wliich have 
been thoroughly treated with water and the moisture adhering to 
them partly removed with the aid of bibulous paper applied edgewise 
as it is wlien the stigma has not come in contact with Mater. 

THE APPLICATION OF WATER TO ALL FLOWERS. 

For the removal of pollen wliich may have been deposited upon the 
stigma of a flower previous to pollinating, water should be used in 
every case where the flower has been exposed through inadvertence 
or otherwise to the visits of insects. Its use in such a case, if it be 
applied within a certain period after the pollen is deposited, is desir- 
able, as it will render the operation of crossing with another flower 
more certain, because if pollen is present on the stigma of a (lower, 
especially if the pollen be of tlie same variety or species as the flower 
which it is desired to use as the seed bearer, its own pollen will in 
jnany cases take effect in preference to the pollen of the flower of a 
separate species or variety. 

Another case may be mentioned in wliich this adjunct to perfect 
emasculation can be used advantageously. It sometimes happens 
that an operator comes across an open flower of some Idnd which he 
may wish to cross, with the stamens already deliisced and the stigmas 
well covered with pollen. If the pollen has been deposited on the 
stigmas for only a short time,- in most flowers every grain can be 
removed effectively by the aid of the depollinating method herein 
described. In the case of lettuce the flowers have been depolHnated 
after the pollen had been in contact with the stigma for an hour and 
a half and a successful cross has followed. 

CROSSING ALFALFA. 

WORK ACCOMPLISHED IN THE PAST. 

For the purpose of demonstrating how the new method of preparing 
flowers for crossing can be applied to a wide range of subjects, alfalfa 
may be taken as an example. While it is true that alfalfa crosses 
and hybrids are effected by insects, the genus is an exceedingly 
difficult one to deal with by ordinary methods of emasculation, and 
there is probably no record of intentional crosses among the many 

107 



CROSSING ALFALFA. 17 

forms of Medicago sativa^ or hybrids between it and other species, 
if we except those of Urban,'' who succeeded in making reciprocal 
crosses with Medicago sativa and M. falcata in 1S77. The work of 
Urban, however, was evidently done without taking the necessary 
precautions to preclude the possibility of error, as the pollination was 
a crude imitation of that effected by insects. 

We can not afford to relegate the crossing of the varieties of this 
increasingly important plant to insects or to risk pollen of unknown 
or undesirable forms on the plants we wish to cross. If we were to 
copy the insect method, we should, of course, get crosses, but we should 
remain as much in the dark concerning the parentage of the seedlings 
as we have been in the past. 

PECULIAR FEATURES OF THE WORK. 

None of the species and varieties of alfalfa sets seed from self- 
pollination if the flowers remain untripped (PI. II, fig. 1,^). The 
pollen in the untripped flower, being of a slightly adhesive nature, 
does not get an opportunity to move after being discharged from the 
anthers while still within the closed keel, and after the dehiscing 
period the surface of the stigma is protected from it by being close 
against the keel. This is the case with the flowers of most of the 
varieties, but there are forms the flowers of which often have the stig- 
mas completely hidden by the pollen (see PI. Ill, C), and yet even 
these do not set seed if the flowers remain untripped. 

When, however, the flower is tripped (PL II, fig. I, B), either by 
drawing the closed hand along the raceme or by snipping the indi- 
vidual flowers with the forceps, this action releases the column from 
its imprisonment within the keel and permits it to spring upward 
with a very rapid movement. In doing so the pollen grains are throw^n 
on the banner in large numbers and the stigma falls with force among 
them, causing a mass of the grains to be embedded in it (PL II, 
fig. 1, B). This action usually results in fertilization. 

When the flowers are visited by certain insects, the upper part of 
the sexual column falls with considerable force on the imder part of 
the insect. The stigma in this case is then partly pollinated with 
})ollen from the same flower, from other flowers on the same plant, 
or from flowers of other })lants of the same variety or from other 
varieties, or from pollen of other species previously deposited on 
the body of the insect. 

a The botanical history and nomenclature of this species have been discussed in pre- 
vious publications of the Bureau of Plant Industry; by C. S. Scofield in Bulletin 131, 
part 2, "The Botanical History and Classification of Alfalfa," and by Charles J. Brand 
in Bulletin 118, "Peruvian Alfalfa: A New Long-Season Variety for the Southwest." 

i> Urban, I . Verhandlungen des Botanischen Vereins der Provinz Brandenburg, vol, 
19, p. 125. 1877. 

11026— Bull. 167—10 3 



18 NEW METHODS OF PLANT BREEDING. 

OLD METHODS OF CROSSING ALFALFA. 

Perhaps the method first used in crossing alfalfa, at least so far 
as can be ascertained, consisted in introducing a sharjiened piece of 
wood, resembling in shape the proboscis of a bumblebee, into the 
suture formed by the blades of the keel of the pollen bearer. The 
piece of wood was dusted over with pollen secured by allowing a 
sexual column to trip on it. It was pushed into the suture of the 
flower of the proposed seed bearer, and the resulting tripping of the 
column caused the stigma to come in contact with the pollen already 
secured on the piece of wood, the supposition being that, in some 
cases at least, foreign pollen is prepotent over that of the seed bearer 
on its own flowers. 

The second method — one which the writer tried several years 
ago — consists in emasculating the flowers in the bud stage, but as 
the anthers dehisce before the buds expand the operation must be 
performed when the buds are quite small, and the danger of bruising 
the flower enough to cause it to wither is great. This operation is 
easily performed with the aid of a binocular dissecting microscope, 
but even when the parts of the flower are left uninjured the method 
is clumsy and exceedingly uncertain. 

Another method which involves a considerable element of uncer- 
tainty consists in planting one or more plants of a known variety in 
the midst of a large field of another variety. These plants are used as 
seed bearers and the work of pollination is left to the insects. 

Thus it will be seen that when a cross of known ancestry is desired 
between two varieties of alfnlfa the chances of securing it by methods 
heretofore in vogue are very remote. 

NEW METHODS DEVISED BY THE WRITER. 

A few years ago, while investigating methods of crossing alfalfa 
and tr3ang to cross a hardy form of Peruvian alfalfa with a variety 
from Turkestan, it was found that there are at least three variations 
in the method of compelling this ])lant to capitulate readily to the 
wishes of the plant breeder. 

DEPOLLINATION BY WATER. 

The first method to be described requires close attention to details. 
The tools and other necessary material are as follows : Four pairs of 
forceps, three of them self-closing; a pair of scissors (see fig. 1, A); a 
few pins; a small chip blower such as dentists use (see fig. 2, A and B) ; 
a vessel of water; and some pieces of good blotting paper. 

The operations of dei)ollinating and applying pollen to the stigma 
can be performed satisfactorily with the unaided eye, but the operator 
should take his first lesson with the aid of a low-power binocular 

167 



CROSSING ALFALFA, 19 

dissecting microscope. The magnification should not be higher than 
8 diameters. 

Three or four flowers on a raceme shoidd be selected for crossing. 
The others may ])e cut off, although this is not necessary if they be 
tripped and the surj)lus pollen removed by wasliing with water. 
However, when all but three of the flowers on a raceme are removed, 
those intended for crossing can be reached moi-e easily. The age 
of the flowers used as seed bearers for crossing seems to make little 
difference, provided they do not show signs of withering. It is per- 
haps the safer j)lan to select those flowers near the center of the raceme 
just when the buds at the end of the raceme are about to expand. 
The flowers should not be mutilated in any way, and of course should 
be handled as little as possible because of their delicate nature. 

The first requisite consists in having pollen from the male ])arent 
at hand ready to be applied to the prepared stigmas. To do this 
most conveniently, as the flowers can not very well be manipulated 
with the fingers alone, it is desirable to have three pairs of forceps, 
one for each flower that is to be pollinated. Self-closing forceps are 
best, because they hold firmly the sexual column (PI. Ill, C and D) 
used in pollinating. Take a flower from. a raceme of the male })arent, 
bend down and secure the banner between the tips of the thumb and 
the forefinger, then ])ress wntli a pin or dissecting needle sidewise 
against the suture of the keel, beginning at the base and gradiuxlly 
drawing upward. If this o})eration is done carefully, the column will 
come out gently without disturbing the pollen from the anthers. 
When the flower has been trippetl or exploded in this way, the ter- 
nunal part comprising the stigma, with the masses of pollen surround- 
ing the empty anthers closely arranged around it, hangs toward the 
operator free from contact with anything. With the aid of the self- 
closing forceps, sever the column from the flower, laying the columns 
aside ready to be applied to the stigmas of the flowers of the seed 
bearer when the latter is depollinated. 

Now comes the inost critical part of the operation, and the amount 
of skill with which it is performed determines the success or failure 
of the work. It must be understood that in the flower to be used as 
the seed bearer the stamens dehisced while the flower was in the bud 
stage, perhaps a day or two previously, and the pollen lies in masses 
all around the soft stigma (PI. Ill, C and D), but still incompetent in 
that position to perform the acts of pollination and fertilization while 
the column is untripped. It should be the aim of the operator to 
trip the column in a manner that will cause a minimum disturbance 
of the arrangement of the pollen and prevent the terminal part of the 
column containing the sexual organs from springing with considerable 
force on tlie awaiting banner, thereby embedding a large number of 
its own pollen grains in the soft, pulpy stigma. 

167 



20 NEW METHODS OF PLANT BREEDING. 

With this end in view, grasp one of the flowers gently but securely 
between the tips of the thumb and forefinger, with the back of the 
keel resting against the tip of the index finger. Cut an ordinary 
small-sized pin or needle in two, take the pointed end between the 
thumb and index finger of the free hand, place the half pin or needle 
against the lower part of the suture of the keel, and press gently 
against the keel, bringing the pin or needle up to the central part or a 
little beyond it, increasing the pressure gradually. This will compel 
the sexual column to alter its position, or "trip," gradually as the 
gentle pressure of the pin retards or prevents its springing with force 
enough to disturb the arrangement of the pollen grains around the 
stigma. Allow the pin supporting the sexual column to come gently 
toward the awaiting banner. It will then be found that, with the pin 
resting on the banner, the fingers may relax their hold, the pressure of 
the column toward the banner keeping the pin in place; and owing 
to the position of the pin, for the time being the terminal part of the 
sexual column, consisting of stigma and an abundance of pollen 
around it, is prevented from pressing on the standard, as it is about 
one thirty-second to one-sixteenth of an inch above it. (PI. II, fig. 1, 
C, and PI. II, fig. 2.) This gives the opportunity for the removal of 
the pollen grains b}^ the use of a jet of water from the chip blower. 

The action of the water effectually depollinates the flower without 
causing the least injury (PI. II, fig. 1, Z>); in fact, the jet may be of 
sufficient force to remove even the empty anthers without injury to 
the stigma. (PI. Ill, E'and F.) However, the first few flowers oper- 
ated on by the beginner should be examined before proceeding with 
the pollination to ascertain if the treatment given has been sufficient 
to depollinate the flower thoroughly. 

After the jet of water has been applied there will be a considerable 
quantity of moisture covering the difi^erent parts of the flower, espe- 
cially the empty anthers and stigma. This is immediately removed 
by touching these organs and other parts of the flower with a piece of 
blotting paper applied edgewise. 

When this operation has been completed the exposed stigmas are 
pollinated in the following manner: Take one of the self-closing 
forceps, holding one of the previously prepared sexual columns from 
the flowers of the male parent, and with the stigma pointing upward 
push the end of the column containing stamens and freed pollen 
closely surrounding the stigma under the end of the column which 
has been depollinated, giving it a very slight circular movement to 
make certain that the large masses of pollen come in contact with the 
soft stigma of the depollinated flower. Wlion this has been satisfac- 
torily done, take hold of the supporting pin by the blunt end and 
gently withdraw it; the column then assumes its place on the banner 

167 



CROSSING ALFALFA. 21 

with the stigma closely pressed against its surface (PI. II, fig. 1, F), 
and a goodly number of pollen grains are embedded in the soft stig- 
matic surface. When the supply of pollen is unlimited a number of 
flowers may be tripped over a watch glass and the pollen applied to 
the stigma with a small brush, the hairs of which are held together 
with a weak sirup of sugar and water. 

If the details described are carried out in a painstaking way, all 
that is done simply consists in substituting pollen from another variety 
for that which originally surrounded the stigma of the flower of the 
proposed seed bearer. 

The operation is performed in much less time than it takes to 
describe it, and the operator is rewarded by a fairly high percentage 
of successful crosses. The first time the writer tried this method with 
two distinct varieties of Medicago saliva more than two-thirds of the 
flowers worked set seeds. 

The second method of crossing alfalfa also involves depollination 
with the aid of a jet of water on the dehisced stamens, but it has now 
been discarded in favor of that just described. It is a simpler opera- 
tion, requiring less delicate manipulation, but the percentage of suc- 
cessful crosses by it is very low. Besides, it involves the mutilation 
of the floral envelope and the exposure of the pollinated stigma to the 
atmosphere instead of allowing it to assume its natural position on 
the banner of the flower after being pollinated. 

By this method all the flowers on a raceme may be used. First, 
by the aid of the scissors shown in figure l^A, cut off all of the unopened 
buds and the banner of each flower left on the rachis. The reason 
for removing the banner is that when the flower column is trippe<l 
the position of the sexual column is altered so as to free it from con- 
tact with anything and to render it readily accessible. 

The depollination of the flower thus becomes a very simple prob- 
lem. The sexual column, being still imprisoned within the keel, is 
best tripped by a very light snip given by a pair of forceps, care being 
taken to place the tips of the forceps at a point near the base of the 
column so that the stamens and pistil are not interfered with in with- 
drawing. The sexual column being now free from the keel, the latter, 
together with the wings, should be cut off. 

A small jet of water is then trained on the sexual organs from a 
water bulb or chip blower (see fig. 2, A and B)\ the stream should be 
quite gentle at first, followed with just sufficient force to remove both 
pollen and empty anthers. This will facilitate an easy approach to 
the stigmas when pollinating. Examine the stigmas with the aid of 
a lens to ascertain if all of the pollen has been removed ; then remove 
the surplus water by applying lengthwise a piece of thick and very 
bibulous blotting paper. The flowers are now ready to be pollinated. 

1G7 



22 NEW METHODS OF PLANT BREEDING. 

In preparing the sexual column of the pollen-bearing flower so that 
the pollen may be easily and quickly applied to the stigmas of the 
depollinated flowers of the seed bearer, detach one flower at a time 
and pollinate as described for the first method of crossing. If the 
pollinated stigmas are left exposed to the air, fertilization takes place 
only in a very small percentage of the flowers. They give a higher 
percentage when protected by a small paper bag, or each raceme may 
be placed inside of a test tube and kept in place by a small wad of 
cotton for twenty-four hours after pollination, the test tube being 
tied to a support and shaded from direct sunlight. 

DEPOLLINATION BY COMPRESSED AIR. 

The third method by which alfalfa and other flowers have been 
successfully depollinated is the use of compressed air. Contrary to 
expectation, this has no injurious efl'ect on the tender parts of the 
pistil. 

The parts of the flower are prepared in a manner similar to that 
described in the first method. The current of air is obtained from 
a small cylinder into which air is pumped to an indicated pressure of 
20 pounds. The nozzle of the air tube is held about half an inch from 
the terminal part of the colunm by a helper; the full force is turned 
on just when the column is about to spring from the keel and is con- 
tinued for ten or fifteen seconds after resting on the pin. 

Pollination and subsequent treatment are performed in the same 
manner as given for the first method. 

Fertilization following this method is satisfactory, but the percent- 
age of successful crosses is not as high as in the first method described. 

In depollinating large flowers of other genera having pistils that 
may be easily injured, it is very helpful to remove large quantities of 
pollen previous to the more thorough work by a jet of water from 
the chip blower. 

THE GROWING OF THE PLANTS AND THEIR CARE. 

In order to have the parent plants of alfalfa intended for crossing 
thoroughly under control, they should first be raised from seeds to 
ascertain if the varieties come true. The i)lants to be crossed should 
be grown in a cool greenhouse and when of sufficient size i)ut in large 
pots, as then they are less apt to become suddenly dry at the roots. 
Good fibrous loam and a little rough sand make a good soil for pot 
culture. To prevent soviring of the soil, jilace some large potsherds 
over the drainage hole, and over these place some half-rotted leaves. 
Ram the soil moderately firm around tlie roots, leaving sufficient 
space to give enough water at a time to last for two or three days. 

167 



CROSSING LARGE-FLOWERED LEGUMES. 23 

It should bo the aim of the cultivator to have the plants in bloom 
about the end of March or the beginiiin<2; of April. At that season the 
absence of insects will render the work easier of accom])lishment than 
when grown outdoors. Under outdoor conditions the plants would 
require to be protected by wire or cloth screens to exclude })ollinatin2; 
insects. Several specimens of each variety to be worked with shoidd 
be grown to make certain of having some of them in bloom at the 
proper time. A strong plant of the variety to be used as the seed 
bearer should be selected. 

RAISING LARGE QUANTITIES OF SEED FROM A CROSS. 

When a promising variety of alfalfa has been secured by crossing, 
the problem of how best to secure a ({uantity of seed to sow a large 
area is undoubte'dly a serious one. In the first })lace, the plants slioukl 
be tested thoroughly to ascertain if they are superior to existing forms. 
The crosses obtained so far do not seem to vary much in the second 
and succeeding generations when seed is saved from flowers tripped 
by the hand. Those that prove of value from a single cross, the indi- 
viduals of which are evidently alike, should be pi-opagated vegetatively 
and the progeny of each ])]ant ke])t separate till ])lanted out in the 
field, when they may l)e niixed for cross-pollination. The cuttings 
will root satisfactorily in a cold frame if kept closed for a few days. 
It is possible by this method to root several hundred cuttings during 
the summer, beginning with a single mother plant in the spring, but 
it must be understood that these cuttings originating from a single 
mother are to be considered as one plant; that is,if'seeds set poorly on 
the mother plant as a residt of self-pollination by artificial tripping, 
all the plants propagated asexually from the original wiU have the 
same peculiarity. If the asexually propagated progeny be planted in 
a field a safe distance from other varieties, the probabilities are that 
the plants from the resulting seed will come true and the strain be 
established. In this way a much larger crop of seed can be secured in 
a given time than if one depends altogether upon seeding the original 
individuals of a cross. 

CROSSING LARGE-FLOWERED LEGUMES. 

In crossing varieties of legumes which come true from seed resulting 
from self-pollination, it is not necessary to work with a large number 
of flowers. Carefid manipulation of a few will give all the possible 
results with any two varieties, and usually the operator will get more 
varieties than he desires in the second and subsequent generations. 
The flowers of such plants as Phaseolus, wStizolobium, Vigna (PI. IV, 
fig. 1), Pisum, and Lathyrus should be emasculated in the bud stage 
and before the anthers shed their pollen. The operator before under- 



24 NEW METHODS OF PLANT BREEDING. 

taking to cross two varieties should have a j^erfect knowledge of the 
parts of the flower. 

The idea of having large models of the various flowers of the prin- 
cipal garden and field crops in agricultural colleges and schools is a 
good one. It enables prospective plant breeders to become familiar 
with the structure of the common flowers and shows what is necessary 
to be done in preparing flowers for crossing more quickly than the 
study of the flowers themselves or the use of illustrations made by 
others. Many of the flowers of forage plants and vegetables are so 
minute that it is with difficulty that they are emasculated even with 
the aid of a good dissecting microscope. This is the case with all the 
species of Melilotus and a goodly number of the species of Medicago 
and Trifolium; and the student, having the forms and structure of 
the flowers continually in his mind, will be better prepared to cope 
successfully with plant-breeding problems. 

Among the large-flowered legumes, varieties of which it is desired 
to cross, the cowpea may be chosen as a good example in order to show 
how the flower is manipulated previous to pollinating. In the evening 
it is found that the buds which will expand the next morning are quite 
large and easily manipulated in emasculating. (PI. IV, fig. 1, A.) 
Hold the bud between the thumb and the forefinger, with the keeled 
side uppermost (PI. IV, fig. I, B); then run a needle along the ridge 
where the two edges of the standard unite. Bring down one side of 
the standard, securing it in position with the thumb ; then do the same 
with one of the wings, which will leave the keel exposed. This must be 
slit on the exposed side about one-eighth of an inch below the bend in 
the keel and continuing along until about one-sixteenth of an inch from 
the stigma, which can be seen through the tissue of the keel. Bring 
down the section of keel and secure it under the end of the thumb. This 
will expose the immature stamens, 10 in number. (PI. IV, fig. 1, B.) 
With a fine-pointed pair of force])s seize the filaments of the stamens 
and pull them out, counting them as they are removed to make certain 
that none are left. (PI. IV, fig. 1, C.) Allow the disturbed parts of keel, 
wings, and standard to assume their original positions as far as possible. 
Next detach a leaflet from the plant, fold it once, place it over the 
emasculated flower bud, and secure it in position with a pin or tooth- 
pick. This will prevent the bud from drying out before the stigma 
matures sufficientl}^ to be pollinated from a flower of a difl'erent 
variety next morning. If the stamens are removed without altering 
the position of the pistil (PI. IV, fig. 1, C) or injuring it in any way 
and pollen is applied the morning after the flower is emasculated 
(PI. IV, fig. I, D), in nine cases out of ten they will set seed; and if 
none of the anthers were ruptured in their removal, the resulting 

167 



CROSSING IN LABGE AND SMALL NUMBERS. 25 

seedlings will have some of the characters of both ])arents. If the two 
parents have spotted seeds and the seed bearer, for instance, be the 
well-known variety New Era (PI. IV, fig. 2, A) and the pollen bearer 
the eqnally well-known \^^iippoorwall variety (PI. IV, fig. 2, B), the 
seeds resnlting from the first-generation plants wall have the markings 
of both parents on each seed, giving a beautifnl example of crossing in 
the seed itself. (PL IV, fig. 2, C.) In the second generation we have a 
strange combination. Abont nine parts of the resnlting seeds are like 
those of the first generation, three parts like Whippoorwill, three 
parts like New Era, and one part self-colored, resembling the lighter 
or ground color of the straight ^Tiippoorwill seeds; but in the first 
three lots, although the series are easily classed, there are upward of 
30 variations in color alone, and many more wdien we take form and 
size into consideration. In subsequent generations they again vary 
until by following defined rules we get new fixed types. 

However, the variations in cowpea crosses are not always so very 
apparent, especially when two varieties having seeds of the same 
color are selected as parents. While there are great differences in the 
other characters of the progeny, such as foliage, early and late ripen- 
ing, vining habit, upright growth, and disease resistance, the seeds 
differ from the parents and among themselves apparently only in 
size and shape; and while in the first-mentioned cross one could 
pick out dozens of dissimilar seeds in the colors alone, three or four 
variations in size and shape are about all that the operator may 
expect from crossing varieties the seeds of which are similar in color 
but vary in size. 

In the condition of the mother plant at the time of pollination there 
is fortunately some choice which makes for a high percentage of 
successfid pollinations. It will be found, especially with the cowpea, 
that young plants allowed to fruit in 5-inch pots set seed with greater 
certainty than will rampant-growing plants in large pots. Again, 
old plants in large pots break freely into growth, but not of a viny 
nature. This growth produces flowers in abundance, and jxxls 
form with great freedom either fiom their own pollen or when crossed 
with ])ollen from other varieties. 

CROSSING IN LARGE AND SMALL NUMBERS. 

A matter of impoi-tance in plant breeding an<l one which does 
not receive the attention it deserves from the practical breeder is 
the grouping of varieties into at least two classes for somewhat dif- 
ferent treatment in crossing. In the first division all the ])lants 
we now call varieties, which come true from seed, no matter how they 
originated, may be termed artificial species. This division includes 



26 NEW METHODS OF PLANT BREEDING. 

garden and field crops, such as lettuce, cabbage, and turnips; radishes 
and others of this family; onions and other plants of the same natural 
order; carrots, celery, parsley, and parsnips; the cereals; varieties 
of alfalfa, and many others which come true from seed and are only 
propagated sexually. With these there is no necessity for raising 
many -individuals of the first generation. If the breeder succeeds in 
getting a desirable cross between two well-defined kinds, a few indi- 
viduals of the first generation are enough, provided the work of emas- 
culation or depoUination and the application of pollen to the flower so 
treated is not carried out in a perfunctory manner. The individuals 
of the second generation, if they are sufficiently numerous, will give 
the variations from which to choose selections for perpetuating. 

The second great division mcludes those plants which do not 
come true from seed or at least have never been bred to reproduce 
in that manner. The treatment in crossing is different from that 
which should be accorded the sexually propagated varieties, in 
that large numbers of the first generation are necessary, so that 
the chances of securing improved forms will be greater in propor- 
tion to the number of seedlings raised from any one cross. Nearly 
all fruit and nut trees, grapevines, bush fruits, strawberries, and 
potatoes are included in this class; also many florists' flowers, such 
as roses, carnations, gladiolus, dahlia, fuchsia, chrysanthemums, and 
pelargonium. When the desired improvement is attained by crossing 
any two varieties, one plant of the improved form is sufficient to 
start with, and that is increased vegetatively, i. e., by cuttings, bud- 
ding and grafting, layers, bulblets, cormlets, etc. 

In this second division, when breeding improved forms by crossing 
is attempted we look for results in the first generation; consequently, 
the number of flowers pollinated must be large, so that the seed 
ripened will be in quantities large enough to give the necessary 
variation in the resulting seedlings. The plants mentioned above 
which are propagated asexually are all hybrids, crosses, or sports 
which have never been bred sufficiently to come true from seed ; thus, 
when any two plants of distinct varieties are crossed we never can 
tell exactly what the progeny will be like, and it is as a rule so very 
varied that if we get one seedling in five thousand possessing charac- 
ters superior to either parent we are doing well. 

HYBRIDIZING SPECIES. 

IIELIANTHUS HYBRIDS. 

It ma}^ be necessary at times to hybridize two natural species. 
If a hybrid is raised, the probabilities are that it will not set seed 
with its own pollen. This was the case in a hybrid recently raised 

167 



HYBRIDIZING SPECIES. 27 

between Helianthus argophyllus and H. dehilis, the latter being the 
pollen-bearing parent. The plants, although subjected to the best 
treatment, did not set a single seed from their own pollen or from 
pollen applied from one flower head to the stigmas of another on the 
same plant; nor was a single seed set on a plant the flowers of which 
were pollinated with pollen taken from flowers on separate plants; 
but when a flower of the hybrid was pollinated with pollen from the 
male parent, seeds were produced freely. These when sow^n and tlie 
plants put in the open ground also seeded very abundantly; the 
flowers resulting from these seedlings were much finer than those of 
the parents or any of their forms. It remains to be seen, however, 
just how the third generation will turn out, as in the seedlings of this 
generation, now only a few inches high, the variation of the foliage is 
considerable. 

GRASS HYBRIDS. 

In hybridizing two species of grass lately the results obtained 
would indicate, in this instance at least, that large numbers of hybrid 
seedlings are not necessary in the first generation of grass hybrids. 
Out of 13 seeds secured, 10 germinated, and no two plants are 
alike; in fact, the variation in the progeny of the first generation is 
moi'e marked than in any second-generation seedlings of any other 
cross between two varieties with which the writer is familiar. The 
parents were Poa aracJin'ifera and P. j^ratfiisis, the latter being the 
pollen bearer. The seed l)earer was a hermaphrodite plant and the 
only one out of about 400 seedlings. 

The flowers of the seed bearer were thoroughly treated with water 
each morning until the crop of stamens was exhausted. A very 
large quantity of pollen from P(Xi 'pratensis was secured by cutting 
half an armful of culms of P. pratensis when in bloom; these were })ut 
in a vessel of water in the evening. Next morning the stigmas of 
P. arachnifera were thoroughly pollinated by taking one handful 
at a time of the culms of P. pratensis and shaking them over the 
depollinated stigmas of the Texas bluegrass. This was done in a 
greenhouse; the stigmas were almost hidden by the pollen. Only 1.3 
seeds resulted, but these were more than enough, as each of the 
progeny might w^ell have been taken for a new species. 

Each of the 10 seedlings was propagated by division and 100 plants 
of each put out in the field. No seeds were produced, as the pollen 
was imperfect; not a single grain was found in good condition. 

Pollen from Poa pratensis was again applied in 1908, and the 
plants seeded abundantly. The resulting seedlings are exceedingl}^ 
varied. Some have long, broad leaves; others short and broad, 
narrow and short, or narrow and long leaves. 

1C.7 



28 NEW METHODS OF PLANT BREEDING. 

CROSSING CULTIVATED VARIETIES ON NATURAL SPECIES. 

PANSIES. 

To show what might be expected in renewing the vigor of some 
varieties by crossing them on wild progenitors, it may be permissible 
to mention some work in the improvement of the common pansy 
in an attempt to enable it to better withstand our hot summers. 
Some time ago a number of plants of Viola tricolor were found growing 
luxuriantly in southern California in hot and dry places. Even 
far down in the Imperial Valley, where the temperature frequently 
reaches a stage unlieard of in the East, the plants seemed at home. 

The idea suggested itself that this plant might be of use 
in imparting heat-resistant characters to the cultivated pansies. 
Plants were raised from the seed gathered and pollen from a strain 
of pansies applied to the stigmas of the wild plants. Some of the 
flowers of the first-generation progeny are shown in Plate XIV. 
The petals were removed from the flowers of the wild plant and 
their stigmas cleared of pollen with the aid of water previous to pol- 
linating. All the plants secured have fair-sized flowers, more or 
less resembling in color and markings those of the wild type. The 
foliage more closely resembles the mother than it does the father. 
Recrossing with pollen from a good strain the present season will 
probably give the desired size next season. 

DAHLIAS. 

The original Twentieth Century dahlia was used in pollinating 
a new species from Mexico four years ago. This species has very 
small, bright-red flowers, and the stems are exceedingly long. The 
larger and very rough leaves are produced near the crown of the 
plant, leaving the principal stems with only very small leaves. The 
flowers of the Mexican plant were depollinated (PI. V, figs. 1 and 2) 
and pollen applied to three of the flowers. Sixteen seedlings resulted; 
the small number of seeds was probably due to the fact that the 
mother plants were growing in small pots in the greenhouse and 
did not flower till after the outdoor crop had been blackened by 
fiost. The pollen was obtained from flowers which had been saved 
and kept in water. 

The resulting first-generation seedlings were strictly intermediate 
between the parents, all of them with very long stems (see PL XV), 
but the varieties were not striking enough in color or size of flower 
to warrant vegetative propagation. The best of them were bagged 
and allowed to set seeds. The seedlings of the following season gave 
a very large assortment of forms, and the colors were more varied 
than those of the first generation. About fifty forms were saved 

107 



CROSS-POLLINATING CLOVERS. 29 

for further crossing and selection. The following suinmei- the best 
of these were crossed with pollen from the cactus and other varieties. 
As a result a few crosses were produced which show that varieties 
may be raised in this way with large and well-formed flowers, some 
of them equal in these respects to some of our best varieties bred 
from plants in cultivation for nearly a century. One of the forms 
with single flowers is shown in Plate XV. 

CROSS-POLLINATING CLOVERS. 

To pollinate clover flowers artificially may seem a difficult opera- 
tion on account of their minute and delicate structure, but in reality 
it is even more simple than the manipulation of the flowers of alfalfa. 
Many observations indicate that the flowers of the red clover are 
incapable of self-fertilization when protected from insects, as plants 
which have been tested with tliis end in view have in no case pro- 
duced seeds. It would, however, seem that the emasculation of clover 
flowers is unnecessar}^, because when the keel is pulled forward 
and the stamens disturbed it rarely happens that the pollen comes 
in contact with the stigma. 

When it is desired to perpetuate well-defined varieties by careful 
intercrossing of individuals, the work of transferring pollen from 
the anthers of one plant to the stigmas of another can be rapidly 
and effectively performed in the following manner: Select plants 
of both the proposed pollen and seed bearers which have developed 
flowers under the protection of a wire screen. We can then be 
reasonably certain of the absence of insect interference. Take a 
flower of the pollen bearer between the thumb and forefinger of 
the left hantl, and using the forceps having a flattened pin tied to 
one end, as shown m figure 1, ('\ place the flat side of the pin parallel 
with the standard of a floret, the pin pointing to the base of the 
keel, and tlraw it gently upward. The result will be that many 
grains of pollen will adhere to the flattened portion of the pin. Turn 
the forceps in the hand so that the prongs take the position first 
held by the pin. This must be done carefully so as not to dislodge 
the pollen on the end of the pin. Then with the prongs of the forceps 
snip a piece from the end of the banner of the flower intended to be 
pollinated. This will show^ which of the flowers on a head have 
been manipulated. Next take one of the prongs of the forceps 
and bend down the keel and wings of the floret to be pollinated, 
securing them in a position under the end of the thumb. This 
operation will bring the upper part of the pistil into view. The 
forceps are now turned in the hand to their first position antl the 
pollen carefully applied to the stigma. The operation is concluded 
by restoring the keel and wings to their original positions. 

167 



30 NEW METHODS OF PLANT BREEDING. 

METHODS OF EMASCULATING AND POLLINATING COMMON 

FLOWERS. 

THE ESSENTIAL ORGANS OF THE FLOWER. 

In the greater number of flowering plants there are what are 
usnaU}^ termed male and female organs in each flower. The rose 
(PI. XI, figs. 1 and 2) and canna (PI. IX, fig. 2, A, B, and C) are familiar 
examples. These are called hermaphrodite flowers. 

Other plants have the male and female organs in separate flowers, 
but on the same plant, as in the begonias (PL XII, fig. 1) and the 
genus Codiaeum (PI. XII, fig. 2). Flowers of this nature are termed 
monoecious. 

There is still another class of plants which has the male flowers 
on one plant and the female flowers on another. Examples of this 
arrangement are found in the willows (PL XIII, fig. 1), the aucuba, 
the genus Nepenthes, and commonly in the edible asparagus (PL 
XIII, fig. 2). These flowers are termed dioecious. 

The so-called male organs are the stamens (PL XI, fig, 1, 8ta), 
usually consisting of the filaments, or stalks, and the anthers con- 
taining the powdery material, or pollen. The so-called female organ 
is the pistil (PL XI, fig. 1, P). The lower part is the ovary 
(PL IX, fig. 2, a, o) ; the next part, in some flowers absent, is known 
as the style (PL III, E and F). The terminal part, that on which 
the pollen is deposited, is the stigma (PL III, E and F; PL IX, fig. 

PREPARATION OF FLOWERS TO BE POLLINATED. 

In crossing plants which have both male and female organs present 
in the same flower (PL XI, fig. 1) the principal point to be kept in 
view is the removal of the anthers from the flower which is chosen 
as the seed bearer before the pollen is ripe; this is to prevent self- 
pollination of the flower. It is also necessary to prevent pollen 
from other flowers on the same plant or from flowers on other plants 
of the same variety or species gaining access to the stigma of the flower 
to be cross-pollinated. To this end it is always advisable to have 
isolated plants for seed bearers. 

A few of the flowers or as many as can be conveniently worked 
at one time may be selected for crossing, and the others removed. 
The selected flowers should be covered with paper bags, or, better 
still, the whole plant if not too large may be covered with a small- 
mesh wire screen, which will efi'ectually prevent pollination by winged 
insects. 

In some plants the anthers of the flower intended to be used as 
the seed bearer must be removed when the flower is in the bud stage, 

167 



EMASCULATING AND POLLINATING COMMON FLOWEKS. 31 

as the stamens mature long before the pistil (see PI. X, fig. 2). This 
operation in many cases necessitates the mutilation of the petals; 
therefore, emasculation in the bud stage should never be performed 
except in those cases ^vhere the anthers shed their pollen before the 
petals expand. Many plants shed their pollen only after the petals 
expand, as in the rose and the lil}", and this is the safest time to 
remove the anthers provided the flowers have been protected against 
access of pollen to the stigmas. 

In plants like Tecoma grandiflora the anthers dehisce long before 
the flower opens, but the lobes of the stigma are closed and do not 
open until the anthers of the same flower have shriveled. However, 
the pollen grains which lie in the tube of the flower might be brought 
into contact with the stigma; therefore, it is safest to remove the 
anthers before they open. 

With some plants, such as the anthuriums, the stigmas are ripe 
several days l)efore the pollen matures. In this case the anthers 
can not be removed, nor is there any necessity for their removal in 
crossing. The common plantain {PJantago lanceolata) (PI. X, fig. 1) 
is another plant in which the pistil matures a short time before the 
stamens of the same flower, thus insuring cross-pollination. 

Those plants which have the stigmas and the stamens in separate 
flowers on the same plant, as in the genus Begonia and the genus 
Codiaeum (PI. XII, figs. 1 and 2), should have the staminate flowers 
removed before they open and the pistillate flowers inclosed in small 
manila paper bags both before and after pollination, or if the proposed 
seed bearers are growing in pots they should be isolated and screened. 

With plants which have pistillate flowers on one plant and stammate 
ones on another, as in the genus Nepenthes, willows (PI. XIII, fig. 1), 
and asparagus (PI. XIII, fig. 2), it is only necessary to guard against 
undesirable pollen by bagging the flowers before and after pollination. 

REMOVAL OF THE ANTHERS. 

The removal of the anthers in the case of flowers having both 
stamens and pistils is called emasculation. There are various ways 
in which the anthers may be removed. Perhaps the best method 
is to use the forceps shown in figure 1, C, as the most delicate stamens 
may be seized and their anthers removed with this instrument. 
When all the stamens are visible to the eye the process is an easy 
one. When, however, the operator wishes to emasculate a flower 
of a legume (PI. IV, fig. 1) or of any other plant in the bud stage, 
he should know the number of stamens in the flower of each species, 
and the anthers should be counted as they are removed, thus making 
certain of the complete emasculation of the flower. 

167 



32 NEW METHODS OF PLANT BREEDING. 

SECURING POLLEN. 

To have the pollen of a flower to be used in pollmatmg absolutely 
pure, it is necessary that the stamens be protected, both before and 
after dehiscing, by the use of paper bags. To secure pollen in suffi- 
cient quantity to make certain that the stigmas of the proposed seed 
bearer are well covered, the best method is to secure a few flowers 
just before the anthers open, with stems long enough to go into a 
vessel of water. Let the vessel containing the flowers stand indoors 
until the stamens dehisce; then hold that part of the flower on 
which the stamens are situated over a watch glass and gently agitate 
the stamens with a pin. The pollen from a few flowers — of the rose, 
for instance (PI. XI, fig. 2, A) — will fall in sufficient quantity to 
cover the glass. Then place the glass in a small box so that it may 
safely be carried from place to place. Some flowers have pollen 
which can not well be treated in this manner because it clings together 
in masses, as in the cowpea and the lily. 

APPLYING THE POLLEN TO THE STIGMA. 

In those flowers having pollen which clings together and adheres 
to the stamens the pollen is best applied to the stigmas directly 
from the stamens by means of the flattened pin shown in figure 1, C. 
Pollen such as that of the rose should never be applied with a dry 
brush unless there is a large quantity available, as this method 
means the loss of a very large percentage of tlie grains. In carrying 
the pollen from the glass to the stigma the least jar or movement 
of the air causes it to fall from the brush. 

The most satisfactory method of transferring dry pollen is to use 
a very small brush prepared in the following manner: Dip the hairs 
in a weak sirup of sugar and water, draw them between the finger 
and thumb to remove the surplus moisture and to flatten the mass of 
hair, clip off a small portion of the ends so that the hairs will be all 
of one length, and trim the sides, which will result in the hairs sticking 
together. While still damp push the end of the flattened brush 
among the pollen grains, and even the driest pollen will adhere in 
masses. It is thus abundantly and easily applied to the most delicate 
stigmas. The experienced breeder can tell at a glance when the 
stigma of any flower is ready to be pollinated. The stigmas of the 
rose shortly after the petals expand indicate the receptive condition, 
and this may be taken as a guide for the stigmas of most flowers. 

167 



DESCRIPTION OF PLATES. 

Plate I. Fig. 1. — Staininal tul)esand stigmas of lettuce flowers (enlarged 20 diame- 
ters): A, Staminal tube; B, stigma appearing through end of tul^e; C, stigma 
covered with pollen; D, stigma depollinated. Fig. 2. — Depollinating lettuce 
flowers with water from a garden hose. 

Plate IT. Fig. 1. — Flowers of alfalfa (enlarged 5 diameters), showing the method of 
depollinating and crossing used: .1. Untripped and unpollinated flower: B, 
tripped and self-pollinated flower; (', flower showing sexual column rri|ij)e(l 
against a pin, to prevent self-pollination and to provide the opportunity for 
depollination; D, depollinated flower; the operation is performed by training a 
jet of water on the sexual organs while the column is resting on the pin; E, flower 
showing the stigma pollinated with ])ollen from the flower of a distinct variet\- or 
species while the column is still resting on the ])in; F, flower from wdiich the 
pin has been -withdrawn after jioUination. allowing the stigma to press against 
the surface of the banner. Pig. 2. — Raceme of alfalfa flowers (enlarged 6 diame- 
ters). This illustration shows that when the column of the flower is tripped 
the pressure is sufficient to hold a small pin. 

Plate III. Sexual columns of alfalfa flowers (enlarged 10 diameters), showing 
different stages of development: A and B, Columns with anthers just l)efore tlie 
dehiscing stage; C and D, columns with anthers dehisced: E and F, columns 
with pollen and empty anthers removed by the aid of water previous to artificial 
pollination. 

Plate IY. Fig. 1. — Flowers and young ])ods of the oowpea (twice natural size): .1, 
Flower bud showing condition on the evening of tlie day previous to tlic openimr 
of the flower; B, flower in the bud stage, showing how the floral envelope is 
opened to gain access to the stamens for emasculation; (', flower with stamens 
removed, showing the large stigma to the left; 7>, emascidated flower the next 
morning after pollination; E. youni; pod the second morning, showing that 
fertilization has l)een accomplished; F, the same pod forty-eight hours after the 
pollination of the flower. Fig. 2. — Seeds of cowpea parents and of a first-generation 
cross (enlarged 2\ diameters). ,1, New Era; /?, Whippoorwill: (\ New Era 9 X 
Whip])oorwill $ . 

Plate V. Fig. \.—l>iihliu chisolniii. (enlarged 4 diameters), showing disk florets 
before depollination. The stigmas are densely covered with pollen. Fig. 2. — 
DnhVui chisolniii (enlarged 4 diameters), showing disk florets after depollination 
Ijy a jet of water. 

Plate VI. Fig. 1. — Disk florets of the greenhouse cineraria before depollination 
(enlarged 5 diameters), showing the stigmas covered with pollen. Fiu'. 2. — Disk 
florets of the greenhouse cineraria (enlarged 5 diameters) after depollination 
with water. 

Plate VII. Fig. 1. — Flower of dahlia (enlarged 5 diameters), sliowin-; the disk 
florets, the stigmas of which are nearly all covered wdth pollen. The stigmas 
of the inner florets are not fully developed. On these the ])ollen is very abundant. 
Fig. 2.— The dahlia flower (enlarged 5 diameters) shown in figure I, with the 
outer florets depollinated by a jet of water. The stigmas of the inner florets are 
not fully developed. 

n()2(;— Pull. ](i7— 10 .-:; 33 



34 NEW METHODS OF PLANT BREEDING. 

Plate VIII. Fii^. 1.— Dahlia florets (enlar<;ed 10 diameters), showing development 
of the stigmas: .4, Unopened disk floret; B, floret after the staminal tube en- 
veloping the stigma has appeared above the corolla; C, floret with the stigma 
partly protruding from the staminal tube; at this stage it is thickly covered with 
pollen; D, floret with the stigma still farther advanced; the upper part of the 
staminal tube is seen near the base of the stigma; E, floret with the stigma fully 
developed and covered with pollen; F, floret with the stigma depollinated with 
water. Fig. 2. — Dahlia florets (enlarged 6 diameters), before and after depoUi- 
nation: A, Disk florets, showing the stigmas covered with pollen: the staminal 
tubes have been pulled within the corollas; B, florets with the stigmas depollinated 
by water. 

Plate IX. Fig. 1.— Disk florets of Helianthus (enlarged 5 diameters), showing dif- 
ferent stages of development: A, Floret in bud stage; B, floret, showing staminal 
tube inclosing stigma, the upper part covered with pollen; (', floret (twenty- 
four hours later), showing the stigma covered with pollen and the staminal tube 
partly drawn within the corolla; D, floret with the stigma depollinated; this is 
done when the floret has reached the stage shown in B. Fig. 2.— Flowers of 
Carina indica (natural size), showing stamen and pistil in different stages of de- 
velopment. Sta, Stamen; S, stigma; 0, ovary. 

Plate X. Fig. 1. — Flowers(proterogynous^ of Plantago lanceolata, sho\ving pistils ma- 
turing before the stamens: .1, Flower head, showing mature pistils; B, flower head, 
showing a few stamens to the right; (\ flower head, showing \\'ithered stamens at 
the base of the flower spike; D, flower head in a more advanced stage. Fig. 2.— 
P^lower (proterandrous) of Campanula roiumU/oUa (enlarged 3 diameters), show- 
ing stamens maturing before the pistil. .4, Flower bud ; B, flower bud with corolla 
removed, showing large, mature stamens encircling the immature pistil; C, flower 
with portion of corolla removed; the stigma is still immature, the anthers have 
discharged their pollen, and the stamens are wilted and curled around the 
base of the style; D, flower after the corolla has withered and the stigma has 
expanded. 

Plate XI. Fig. 1. — Single tea rose, showing how easily hermaphrodite flowers hav- 
ing large stamens may be emasculated: Sta, Stamens; P, pistils. Fig. 2.— 
I'lowers of roses (natural size), showing method of emasculation: A, Flowers with 
petals removed, showing stamens and pistils; B, flowers with stamens removed, 
showing stigmas ready to be pollinated. 

Plate XII. Fig. 1. — Flowers (mona^cious) of begonia, showing the sexes in different 
flowers on the same plant: A, A, Pistillate flowers; B, B. staminate flowers. 
Fig. 2. — Staminate and pistillate flowers of Codiaeum vancgatum from the same 
plant. A, Male flowers; B, female flowers. 

Plate XIII. Fig. 1.— Staminate and pistillate (dia^cious) flowers of willow from 
different plants: A, Female flowers; B, male flowers. Fig. 2.— Flowers from 
staminate and pistillate plants of Asparagus offirinalis (enlarged 5 diameters): 
A, Pistillate flowers; B, staminate flowers. 

Plate XIV. Flowers from first-generation seedlings of crosses of pansies (natural 
size). VIdIa Iricolov 9 X cultivated forms $ . The row of flowers at the bottom 
is V. tricolor uncultivated. 

Plate XV. Single branch of hybrid dahlia plant. Dahlia chisolmii 9 X Twentieth 
Century dahlia $ . Height of branch 7 feet G inclies, showing very large com- 
pound leaves near the base and long flowering stems. 
KIT 



3ul. 167, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate I. 




Fig. 1.— Staminal Tubes and Stigmas of Lettuce Flowers (Enlarged 
Twenty Diameters). 




Fig. 2.— Depollinating Lettuce Flowers with Water from a Garden 

Hose. 



3ul, 167, Bureau of Plant Industry, U. S. Dept^ of Agriculture. 



Plate II. 




Fig. 1 .—Flowers of Alfalfa (Enlarged Five Diameters^, Showing the 
Method of Depollinating and Crossing Used. 




Fig. 2.— Raceme of Alfalfa Flowers i Enlarged Six Diameters 



Bui. 167, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate III. 




Bui, Irw, Bure.v.i of Plant Industry, U, S, Dpot, of Agricultur 



Plate IV. 




Fig. 1.— Flowers and Young Pods of the Cowpea (Twice Natural Sizei 




Fig. 2.— Seeds of Cowpea Parents and of a First-Generation Cross 
(Enlarged Two and One-Half Diameters'. 

A, Now Kra: B. Whipponrwill: C. New Er.i \ X \Vhiii|iOor\,iII '. 



Bui. 167, Bureau of Plant Industry, U, S, Dept. of Agricultur. 



Plate V. 




Fig. 1. — Dahlia Chisolmii (Enlarged Four Diameters', Showing Disk 
Florets Before Depollination. 




Fig. 2. Dahlia Chio.ji_mii Enlarged Fuur Diameters', Showing Disk 
Florets After Depollination by a Jet of Water. 



3u!. 167, Bureau of Plant Industry, U. S, Dept. of Agriculture. 



Plate V!. 




Fig. 1.— Disk Florets of the Greenhouse Cineraria Before D.epollination 
I Enlarged Five Diameters'. 



's ^ r r-'' - 









«aI 



^%A 




^iM 











'^^h 
^ 






Fig. 2.— Disk Florets of the Greenhouse Cineraria After Depollination 
(Enlarged Five Diametersi. 



167, Bureau of Plant Indujtrv, U, S. Dept, of Agncultur 



Plate VII. 




Fig. 1.— Flower of Dahlia 'Enlarged Five Diameters^, Showing 
THE Disk Florets, the Stigmas of which are nearly all 
Covered with Pollen. 




FiQ. 2.— The Dahlia Flower (Enlarged Five Diameters' Shown 
in Figure 1, with the Outer Florets Depollinated by a Jet 
OF Water. 



167, Bureau of Plant Industry, U S Dept. nf Ai^nculture. PLATE VIII. 




Fig. 1.^ 



-Dahlia Florets i Enlarged Ten Diameters), Showing 
Development of the Stigmas. 




Fig. 2. 



-Dahlia Florets (Enlarged Six Diameters', Before and 
After Depollination 



3ul. 167, Bureau of Plant Industry, U. S, Dept. of Agriculture 



Plate IX. 




Fig. 1.— Disk Florets of Helianthus (Enlarged Five Diameters), 
Showing Different Stages of Development. 




Fig. 2.— Flowers of Canna Indica i Natural Size), Showing Stamen 
and Pistil in Different Stages of Development. 



Bui. 1c7, Bjie.iu nf Plant Industry U, S. Dept of Agriculture. 



Plate X. 



^M 




1 


^^^^^^^^l^^n ''' V^Kr^^^^^l 


^^^^H 




1 




^^H^^^^^l 




1 




^^^^^^^^^^^^^^^^^^^^^^^^^1 




^^K^ 


^ « ■* •■WM' ^BV ji.'^^^B^^^^^^B 


^^^^^^m 


[ -M 


H 






[:| 


i 




^t^^^jjU 


IkT '^ 


1 


^fc iJM^BI' '"^B^^^H 


^^^^^^^^^^^H ^^^1 




■Si 


^^^B K^^^Bit^^^^^^B 



Fig. 1 .—Flowers » Proterogynous* of Plantago lanceolata, Showing Pistils 
Maturing Before the Stamens. 




Fig. 2.— Flower i Proterandrous^ of Campanula rotundifolia i Enlarged 
Three Diameters^, Showing the Stamens Maturing Before the Pistil. 



Bui. 167, Bureau of Plant Industry, U, S. Dept. of Agriculture. 



Plate XI. 




Fig. 1.— Single Tea Rose. Showing How Easily Hermaphrodite Flowers 
Having Large Stamens may be Emasculated. 




Fig. 2.— Flowers of Roses 'Natural Size >, Showing Method of Emasculation. 



Bui. 167, Burea 


J of Plant Industry, U, S. Dept. of Agr 


culture. 


Plate XII. 


■ 


"^^ 




■ 


■ 




L^^'^ J 


H 


^^^ 


-*( jh^^^^^^^hsi 




^^H 


H 




^1 ^^^^^ 


H 


1 


^B f/^^^^^^^^^^^P 




1 



Fig. 1 .—Flowers • Moncecious' of the Begonia, Showing the Sexes in Different 
Flowers on the Same Plant. 











Fig. 2.— Staminate and Pistillate Flowers of Codiaeum variegatum from the 

Same Plant. 



Bui. 167, Bureau of Plant Industry, U. S, Dept. of Agriculture. 



Plate XIII. 




Fi3. 1.— Staminate and Pistillate iDicecious) Flowers of Willow, from 
Different Plants. 




Fig. 2.— Flowers from Staminate and Pistillate Plants of Asparagus 
officinalis (Enlarged Five Diameters'. 



167, Bureau of Plant Industry, U, S. Dept, of Agriculture. 



Plate XIV. 




Flowers from First-Generation Seedlings of Crosses of Pansies 
(Natural Size>. 

]'iol(i tricol'ii- 5 X cultivated forms ,^. The ri)\v (if finwers at the buttom 
is Viola tricolor uncultivated. 



167, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate XV. 




Single Branch of Hybrid Dahlia Plant. 
Pd/iliii (iii.''<jliiiii X X Twontk'lli Criituiy dnlilia ^. 



1 X1)1:X 



T;iR('. 

Air, comprossctl, ust' in (lepollinuling alfalfa, mclhod and rcsuUs 22 

Alfalfa, asexually propagated progeny, results of jilanting 2S 

f-rossing, new methods I S-22 

old methods and results IS 

studies of peculiar features 17 

t reatment 25-2(i 

work accomplished in the ])asl 1 (!- 1 7 

depollination l)y compressed air, method and results 22 

water, methods and results J S-22 

flowers, emasculation, difficulties 24 

interchange of pollen and cause 15 

methods of insect pollination 17 

necessity of testing and method used 23 

Peru\dan, experiments in crossing with Turkestan alfalfa 18-22 

plants for crossing, growing and care 22-23 

results of planting asexually propagated |)rogciiy 23 

rooting, method 23 

seed, failure to set 17 

raising large quantities from a cross 23 

studies in crossing experiments 16-23 

Turkestan, experiments in crossing with Peruvian alfalfa 18-22 

Anthers, definition ., 30 

removal, methods 31 

Anthuriums, emasculation 31 

Asparagus, dia'cious plant, pollination 30, 31 

Asters, method of breeding 1 1-15 

Aiicuba, diojcious plant 30 

Begonia, mona'cious flower, pollination 30, 31 

Brand, Charles J., studies on alfalfa 17 

Breeding, plant , cross-fertilization, definition 13 

emasculation, definition 13 

experiments in crossing and hybridization and results 15 

hybridization, definition 13 

importance of variety grouping 25-26 

new methods, origin 8-10 

studies 7-8 

See ciJfio Crossing, Depollination, Emasculation, llyliridization. 
and Pollination. 

Budding, method of vegetatively increasing jjlants 26 

Bulblets, use in vegetative increase of plants 26 

Cabbage, crossing 25-26 

(Cactus dahlia, experiments in crossing with Twentieth Century dahlia 29 

Canna, hermaphrodite flower 30 

11026— Bull. 167—10^ 5 35 



36 NEW METHODS OF PLANT BREEDING, 

Page. 

Carnation, emayculalion (if flowers 13 

tfeedlinii:^, crossiny 26 

( 'arrotfs, crossing 25-26 

Celery, crossing 25-26 

(Jereals, crossing 25-26 

Cherry, emasculation of flowers 13 

Chrysanthemum, method of breeding 14-15 

seedlings, crossing 26 

Cineraria, method of breeding 14-15 

Clovers, cross-pollination, methods 29 

emasculation, difficulties 24 

Codiaeum, emasculation of flowers 30, 31 

Compositae, emasculation of flowers, obstacles 13-14 

uncertainty of cross-fertilization 14 

I "ormlets, use in vegetative propagation 26 

Cosmos, method of breeding 14-15 

( 'owpea, crossing methods and results 24-25 

difficulty in treating pollen 32 

New Era, crossing experiments 25 

small plants compared with large jilants for seed production 25 

Whippoorwill, crossing experiments 25 

Cowpeas, emasculation, difficulties 24 

Cross-breeding. See Breeding, cross. 

fertilization. See Fertilization, ci'oss. 

( 'rosses, composite flowers, origin 14-15 

Crossing alfalfa. See Alfalfa, crossing. 

cultivated varieties of plants on natural species 28-29 

experiments in plant breeding 15 

large-flowered legumes 23-25 

Cuttings, use in vegetative increase of ])lants 26 

Dahlia, Mexican, experiments in crossing with Twentieth Century dahlia. . . . 28-29 

seedling, crossing 26 

Twentieth Century, experiments in crossing wilh cactus varieties 29 

Mexican species, 

new 28-29 

I )ahliaSj experiments with first-generation seedlings 28-29 

method of breeding 14-15 

1 )epollination, alfalfa, by compressed air, method and results 22 

water, methods and results J 8-22 

definition 8 

flowers, application of water 16 

devices required and description 12-13 

methods and results 14 

tools required and description 11 

lettuce, experiments 9-10 

Emasculation, flowers, common methods 30-32 

Compositse, obstacles 13-14 

definition and method 13, 3 1 

lettuce, experiments and results 8-10 

studies in plant breeding 7-8 

tools required and description 11 

Fecundation, study of method of prevention 8 

ir.T 



IXDKX. 37 

l'\'rtilizat.ioii, cross, delinitioii \'.\ 

Florets, fertilization of flowers 1 :? 1 1 

Flowers, application of water in dej)ollinaliou l(i 

common, emasculating and ixillinatinu, nictliods :U)-3l.' 

composite, emasculation, obstacles \'A~[4 

hybrids and crosses, origin II- IT) 

depoUination and emasculation, tools re((uired and descri])lioii 11 

devices used and descri])tion \2 ]'A 

dia'cious, definition :50 

essential organs :50 

hermaphrodite, definition :U) 

models, use in agricultural colleges and schools 24 

monoecious, definition :«() 

pollination, methods 'A- 

I)reparation for pollination :>() 'A\ 

Fruit trees, seedlixigs, crossing "-'(i 

Fruits, bush, crossing lili 

Fuchsia, seedlings, crossing i-'(i 

Fumigation, protection from insect pollination 15 

Gaillardia, method of depoUination and results N 

Gas, hydrocyanic-acid, use for [)rotection from insect pollination lo 

Gladiolus, vseedlings, crossing 2(1 

Grafting, method of vegetative propagation I'ti 

Grapevines, seedlings, crossing '2{> 

Grass hybrids. «SVt' Hybrids, grass. 

Helianthus argophyllus, experiments in crossing with Uelianlhus debilis l'O L'7 

debilis, experiments in crossing with Uelianlhus argo])hyllus 2l>-27 

method of depoUination and results U 

Hybridization, natural species 2()-27 

)>lant l)reeding, definition 1 o 

experiments and results lo 

preparation of seed and pollen bearing ])arent plants lo 

Hyl)rids, c(miposite flowers, origin H -15 

grass, experiments in crossing 27 

proportion of seeds germinal i Jig 27 

variation of progeny 27 

helianthus, experiments in crossing 2fi-27 

Int rod uction to bulletin 7-S 

J./athyrus, experiments in crossing 2:^-24 

Layers, use in vegetative propagation 2f) 

Legumes, large-flowered, experiments in crossiiig 23-25 

.self-pollinated, ex])eriments in crossing 23-25 

Lettuce, breeding method 14-15 

crossing, experiments 8-10 

varieties 25-20 

depoUination, method 1(1 

forcing, experiments in crossing S-10 

(iolden Queen, experiments in crossing on Grand Rapids lettuce. ... 10 

(Jrand Rapids, experiments in crossing on Golden Queen lettuce 10 

pollen, methods of removal S -10 

pollination, experiments !»- 10 

seeds, experiments in first -generation crosses 10 

167 



SS NEW METHODS OF PLANT BREEDING. 

Liguliflorte, uncertainty of cross-fertilization 14 

Lily, difficulty in treating; pollen ;i2 

emasculation, suitable time 31 

Marigolds, method of breeding 14-15 

Medicago species. See Alfalfa. 

Melilotus species, emasculation, difficulties 24 

Mendel, Gregor, studies in plant breeding 8 

Nepenthes, emasculation 30, 31 

Nut trees, seedlings, crossing 26 

Onions, crossing 25-26 

Organs, essential, oi flowers 30 

Ovary, definition 30 

Pansies, heat-resistant characteristics 28 

wild, experiments in crossing with cvdtivated pansies 28 

Parsle}', crossing 25-26 

Parsnips, crossing 25-26 

Peach, emasculation of flowers 13 

Pelargonium, seedlings, crossing 26 

Phaseolus, experiments in crossing 23-24 

Pistil, definition 30 

Pisum, experiments in crossing 23-24 

Plant breeding. See Breeding, })lant. 
Plantago lanceolata. Sec Plantain. 

Plantain, prolerogyny of flowers 31 

Plants, cross-breeding, studies 7-8 

experiments in crossing cultivated vari(>ties on uatiaal species 28-29 

female organs, description 30 

isolation from insects necessary when selected for pollen 15 

male organs, description 30 

perpetuating, choice of selections 26 

seed and pollen bearing parents, preparation for hybridization 15 

vegetative propagation, methods 26 

Plates, descri j)tion 33-34 

Poa arachnifera, experiments in crossing with I'oa prateusis 27 

pratensis, experiments in crossing with Poa arachnifera 27 

Pollen, application to stigma, necessary conditions 16 

bearers, growth under glass requiretl 15 

preparation of parent plants for hybridization 15 

care of plants from which selected 15 

definition 30 

method of application to stigma 32 

removal from stigma when desired 16 

securing 32 

methods of use in j)lant crossing 8-9 

results of careless selection , 15 

rose, methods of securing 32 

Pollination, clovers, methods 29 

common flo\\ers, methods 30-32 

condition of stigma 16 

flowers, methods 32 

lettuce, experiments and results 9-10 

method and results 20-21 

preparation of flowers 30 

ir.T 



INDEX. 39 

I'age. 

Poj)|)\ , emat^culatiou <>t' Howois 13 

Potatoep, seedlings, t-rossing 26 

Radishes, crossing 25-26 

Rose, emasculation of flowers 1:5, 31. 

hermaphrodite flower 30 

pollination, method 32 

seedlings, note on crossing 26 

Scofield, C. S., studies on alfalfa 17 

Seed, alfalfa, raising large quantities from a cross 23 

bearers, preparation of parent plants for hyhridi/.atiun 15 

Seedlings, characteristics 26 

Stamens, defl nition 30 

Stigma, condition at time of j)ollination 16 

definition 30 

method of aj^plying pollen 32 

rose, time for pollination 32 

Stigmas, protection necessary after pollinat ion 22 

Stizolobium, experiments in crossing 23-24 

Strawberries, seedlings, <'rossing -. . . . 26 

Style, definition 30 

Tecoma grandiflora, experiments in emas( ulation 31 

Thrips. pollen-eating, carriers of pollen 15 

responsibility for impure i)()Ilt'u 15 

Tobacco, emasculation of flowers 13 

Tools required for de]>ollination and emascuhUioii of liuwcrs II 

Trees, fruit and nut, crossing 26 

Trifolium species. !^ee Clover-. 

Turnips, crossing 25-26 

Urban, 1., studies in crossing alfalfa 17 

Varieties, importance of grouping in jdant breeding 25-26 

Vigna species. See Cowpeas. 

Water, application to flowers in di'])(»lliuating 16 

use in depollination of alfalfa, methods and results 18-22 

Willow, dioecious jjlant. pollinat ion 30, 31 

Zinnias, method of breeding 14-15 

107 

o 



[Continued from page 2 of cover.] 

No. 85. The Principles of Mushroom Grooving and Mushroom Spawn Making. 1905. Price, 10 cents. 

86. Agriculture without Irrigation in the Sahara Desert. 1905. Price, Scents. 

87. Disease Resistance of Potatoes. 1905. Price, 5 cents. 

88. Weevil- Resisting .Adaptations of the Cotton Plant. 1906. Price, 10 cents. 

89. WOd Medicinal Plants of the United States. 1906. Price, 5 cents. 

90. Miscellaneous Papers. 1906. Price, 5 cents. 

91. Varieties of Tobacco Seed Distributed, etc. 1906. Price, 5 cents. 

92. Date Varieties and Date Culture iu Tunis. 1900. Price, 25 cents. 

93. The Control of Apple Bitter-Rot. 1906. Price, 10 cents. 

94. Fann Practice with Forage Crops in ^^ estern Oregon, etc. 1906. Price, 10 cents. 

95. A New Type of Red Clover. 190(3. Price, 10 cents. 

96. Tobacco Breeding. 1907. Price, 15 cents. 

97. Seeds and Plants Imported. Inventorj' No. 11. 1907. Price, 15 cents. 

98. Sov Bean Varieties. 1907. Price, 15 cents. 

99. Qiiiclc Method for Determination of Moisture in Grain. 1907. Price, 5 cents. 

100. Miscellaneous Papers. 1907. Price, 25 cents. 

101. Contents of and Index to Bulletins Nos. 1 to 100. 1907. Price, 15 cents. 

102. Miscellaneous Papers. 1907. Price, 15 cents. 

103. Dry Fanning in the Great Basin. 1907. Price. 10 cents. 

104. The Use of Feldspathic Rocks as Fertilizers. 1907. Price, 5 cents. 

105. Relation of Composition of Leaf to Burning of Tobacco. 1907. Price, 10 cents. 
100. Seeds and Plants Imported. Inventory No. 12. 1907. Price, 15 cents. 

107. American Root Drugs. 1907. Price, 15 cents. 

108. The Cold Storage of Small Fruits. 1907. Price, 15 cents. 

109. American Varieties of Garden Beans. 1907. Price, 25 cents. 

110. Cranberry Diseases. 1907. Price, 20 cents. 

111. Miscellaneous Papers. 1907. Price, 15 cents. 

112. Use of Suprarenal Glands in Testing of Drug Plants. 1907. Price. 10 cents. 

113. Tolerance of Plants for Salts Common in Alkali Soils. 1907. Price, 5 cents. 

114. Sap-Rot and Other Diseases of the Red Gum. 1907. Price, 25 cents. 

115. Disinfection of Sewage for Protection of \^ ater Supplies. 1907. Price, 10 cents. 

116. The Tuna as Food for Man. 1907. Price, 25 cents. 

117. The Reseeding of Depleted Range and Native Pastures. 1907. Price, 10 cents. 

118. Peruvian Alfalfa. 1907. Price, 10 cents. 

119. The Mulberry and Other Silkworm Food Plants. 1907. Price, 10 cents. 

120. Productionof Easter Lily Bulbs in the United States. 1908. Price, 10 cents. 

121. Miscellaneous Papers. 1908. Price, 15 cents. 

122. Curly-Top, a Disease of Sugar Beets. 1908. Price, 15 cents. 

123. The Decay of Oranges in Transit from California. 1908. Price, 20 cents. 

124. The Prickly Petir as a Farm Crop. 1908. Price, 10 cents. 

125. Dry-Land Olive Culture in Northern Africa. . 1908. Price, 10 cents. 

126. Nomenclature of the Pear. ICOS. Price, 30 cents. 

127. The Improvement of Mountain Meadows. 1908. Price, 10 cents. 

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130. Dry-Land Agriculture. 1908. Price, 10 cents. 

131. Miscellaneous Papers. 1908. Price, 10 cents. 

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134. Influence of Soluble Salts, Principally Sodium Chlorid, upon Leaf Structure and Transpiration 

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136. Methods and Causes of Evolution. 1908. Price, 10 cents. 

137. Seeds and Plants Imported. Inventory No. 14. 1909. Price, 10 cents. 

138. The Production of Cigar-Wrapper Tobacco under Shade. 190S. Price, 15 cents. 

139. Americau Medicinal Barks. 1909. Price, 15 cents. 

140. '-Spineless" Prickly Pears. 1909. Price, 10 cents. 

141. Miscellaneous Papers. 1909. Price, 10 cents. 

142. Seeds and Plants Imported. Inventory No. 15. 1909. Price, 10 cents. 

143. Principles and Practical Methods of Curing Tobacco. 1909. Price, 10 cents. 

144. Apple Blotch, a Serious Disease of Southern Orchards. 1909. Price. 15 cents. 

145. Vegetation Affected by Agriculture in Central .Vmerica. 1909. Price, 15 cents. 

146. The Superiority of Line Breeding over Narrow Breeding. 1909. Price, 10 cents. 

147. Suppressed and Intensified Characters in Cotton Hybrids. 1909. Price, 5 cents. 

148. Seeds and Plants Imported. Inventory- No. 16. 1909. Price, 10 cents. 

149. Diseases of Deciduous Forest Trees. 1909. Price, 15 cents. 

150. The Wild Alfalfas and Clovcrj of Siberia. 1909. Price. 10 cents. 

151. Fruits Recommended for Cultivation. 1909. Price, 15 cents. 

152. The Loose Smuts of Barley and Wheat. 1909. Price, 15 cents. 

153. Seeds and Plants Imported. Inventory No. 17. 1909. Price, 10 cents. 

154. Farm Water Supplies of Minnesota. 1909. Price, 15 cents. 

155. The Control of Black-Rot of the Grape. 1909. Price, 15 cents. 

156. A Study of Diversity in Egyptian Cotton. 1909. Price, 15 cents. 

157. The Truckee-Carson Experiment Farm. 1909. Price, 10 cents. 

158. The Root-Rot of Tobacco Caused by Thielavia Basicola. 1909. Price, 15 cents. 

159. Local Adjustment of Cotton Varieties. 1909. Price, 10 cents. 

160. Italian Lemons and Their By-Products. 1909. Price. 15 cents. 

161. A New Type of Indian Com "from China. 1909. Price, — cents. 

162. Seeds and Plants Imported. Inventory No. 18. [In press.] 

163. Varieties of American Upland Cotton. ' [In press.] 

164. Promising Root Crops for the South. [In press.] 

165. Application of Principles of Heredity to Plant Breeding. [In press.] 

166. The Mistletoe Pest iu the Southwest. [In press.] 

167, 





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